A complicated process may be monitored by hundreds of sensors. When there is a problem or event with the process, residuals of the problem may be reflected by measurements of many different sensors. While the event may be manifested in one part of the process, sensors monitoring that part of the process will provide values that reflect the event. Sensors monitoring other parts of the process may also sense values that are outside of normal range. With sensors in different parts of the process all reflecting out of range values, it becomes difficult to recognize the actual part of the process that is directly involved in the event. There is a need for a mechanism to help operators of the process understand events that occur.